Recent Macbooks and the new Magic Trackpad 2 have brought Force Touch to the Mac, but many of the things that a Force Touch press does simply map to the existing three-finger tap gesture that's been around for quite a while in OS X.

El Capitan gives this gesture more actions throughout the system with the idea that Force Touch will be used to invoke them, but many of them can be invoked with the old three-finger tap on a non Force Touch trackpad:

Dictionary

This was one of the original three-finger tap actions. In many text areas, this will bring up the Dictionary entry for the word under the pointer. In El Capitan, this now includes tabs in the popup window for Wikipedia, Maps, the iTunes Store and some others.

A neat trick it also does now is to also include any words to the right that are capitalized if the word under the pointer is capitalized. So, tapping on the first word of "Force Touch" will lookup both words together as a term. You can also select the text you want to look up if it's not a single word.

Quicklook

Three-finger tap in a file in the Finder to Quicklook it. Do it again to cancel the Quicklook. This works in other apps like in Calendar, Reminder to see the detail of an item. It''s generally, like "get info", so in Maps, it is different than clicking on a place -- it's like clicking the "i" button after clicking on a place.

Web link preview

You can use this gesture to preview Web links in Safari and Mail (and possibly other apps).

Data Detectors

Three-finger tap also triggers the preview of text highlighted with a dotted outline by the system Data Detectors, like tracking numbers, contact info, phone numbers, etc. rather than clicking on the tiny little downward triangle next to the info.

View an app's open windows

This is an exception in that it doesn't use three-finger tap but the gesture has been around even longer: move the pointer over an open app's icon in the Dock then use the App Exposé gesture or three fingers swipe down (or four depending on how you've configured it). Repeat the gesture to cancel. This is different than when the pointer is not over a Dock icon, in that case, the App Exposé shows the windows for the current app.

There are likely more place than I've listed here that work, some will be just extrapolation of these, since the Dictionary lookup and Data Detectors work in many text areas in many apps. If you find more, please share them in the comments.